Can a group of nodes be saved?
Use shift-right-click to multi-select nodes, or B to border-select a group of nodes and their connections.  Ctrl-C and Ctrl-V (or platform equivalent) will copy and paste nodes across materials.  

NOTE: After pasting some nodes, try moving the nodes around with the mouse.  Blender has a bad habit of pasting node copies exactly on top of existing nodes, and it becomes almost impossible to see that anything has changed.  Slide the new nodes away to reveal old nodes underneath.

Also, consider using Node Groups to avoid having a bunch of duplicated nodes. This way, you can fix problems in a complex node structure and have the fixes apply to multiple materials at once.

A node group can have inputs for customizing in different ways, to make nodes more re-usable in different materials.  You can create a node group just by multi-selecting the nodes and picking Make group or Ctrl-G. Then, get in and out of the node group editor with the Tab key. Finally, you can add references to your node group from other materials, with Add -> Group -> {GroupName}.